Implement `payment.top_up`

[filvecchiato]

Top-ups and payment requests as the provider's worker uses them.

• payment.topUp for the PrivateKey source, with a caller-chosen id and a status stream
• payment.request with a caller-chosen id, AlreadyExists, and PartiallyClaimed in its status
• Hosts serve both through TopUpPlatform and PaymentPlatform
• Partial-claim retries stay with the caller

Done when A provider worker credits CASH into Pocket, and collects CASH from it, with status to the end.
Depends on #1137
Refs runtime/capabilities/payment.rs

[filvecchiato]

• feat(truapi)!: payments by id and balance through host platforms #1314 payment.topUp by id with topUpStatusSubscribe, TopUpPlatform, native top-up callbacks and notify_top_up_status
• feat(truapi)!: payments by id and balance through host platforms #1314 payment.request and statusSubscribe by id through PaymentPlatform